sleep and dreams

The role of the brain in sleep & circadian rhythms

Explain

The SCN detects light from the optic nerve. When sunlight decreases it singles to the pineal gland.

This realises the hormone melatonin which makes us sleepy, melatonin leaves peak in the middle of the night and fall back down towards daytime.

Adenosine build up in the brain during the day it makes us feel tired and gets replaced during sleep

Circadian rhythms are like a body clock that all species have it’s a cycle of psychological and biological processes that fluctuate on roughly 24 hour timetable.

Examples

Some people feel more energetic or alert at certain points during the day and run down at others

For example, larks and owls

Evidence

Michael Siffer lived in a pitch black cave for 63 days and found his circadian rhythm changed to more like a 25 hour cycle thought he still had an internal clock shows we have inbuilt circadian rhythms but our brain has a role of adjusting this rhythm

Non-RM and REM sleep

Non-REM stage one

Relaxed wakefulness drifting off

Brain waves =theta

Easy to awaken muscles jerking can occur

Stage two

Heart rate flows and body temp decrease

Brain waves = sleep spindles and K comple

Block out external stimuli and possible memory consolidation harder to wake

Stage three and four

Deep sleep

Brain waves

People are hard to wake up

Parasomnias occur

REM

Eyes move rapidly under eyelids

Irregular breathing and higher blood pressure

Temporary sleep paralysis

This is when dreaming occurs

Brain waves equal alpha and beta

Evidence

Dammit and kleitman 1957 supports idea of dreaming occurring in REM

Factors affecting sleep drugs

Explain

Recreational and prescription drugs can affect sleep

stimulate drugs have an effect of making people more alert or more awake

they cannot only reduce sleep quantity but also quality of sleep

Example

Caffeine stimulant drug present in coffee, tea chocolate keeps people alert and makes it hard for them to sleep

Cocaine increases wakefulness and suppresses REM sleep and withdrawals often result in sleep disturbance and unpleasant dreams

Cannabis ease of getting to sleep but withdrawal leads to increased difficult sleep and strange dreams

Alcohol depressant of the CNS and can make you feel sleepy changes proportions of NREM and NREM sleep quality compromised as increased awakening

Prescription drugs can interfere with sleep patterns E.G antidepressant drugs temazepam can cause sleepiness

Evidence

Drake et al 2013 caffeine consumed up to 6 hours before sleep may have disturbed effects on sleep

Pollak 2003 higher caffeine intake was associated with shorter nocturnal sleep duration increase sleep distribution and increased daytime sleep

Orbeta et al 2006 reports of feeling tired in morning and having difficulty sleeping was experienced more commonly in those adolescence that have a high intake of caffeine

Factors affecting sleep light

Explain

Zeitgeberts Referred to environmental signals that affect our cardio circadian rhythm and make our brains think that is time to sleep or wake up the most obvious one for sleep being late the SCN is triggered when there is a lack of light which releases melatonin that makes us sleepy if light is there we will be kept awake

Example

Using your phone or iPad before bed may lead to you having a restless night sleep

Evidence

Hysing et a;2015 did correlational study with 10,000 teenagers in Norway and found that bedtime use of electronics was related to shorter sleep duration and longer onset latency (how long it takes to fall asleep)

Figueiro 2014 exposed participants to pausing blue light through closed eyelids and found this suppressed melatonin production they suggests blue light pulses could be used to delay circadian cycles